Sand blasting apparatus



Jan. 28, 1969 Wl MAASBERG ET AL 3,424,386

SAND BLASTING APPARATUS vFiled Feb. 28, 1966 MVK A L W bm/ h \N Y RQ #QN INVENTORS WLFGA/VG MAASBERG KARL SPR/1 KEL United States Patent O W 40,494 U.s. c1. Z39- 427.3 4 Claims im. cl. B651, 7/04 ABSTRACT F THE DISCLOSURE A sandbasting system in which a stream of granular material is passed through a tubular nozzle and water at a pressure of upwards of 50 atmospheres is directed forwardly at this stream of granules from all around the latter in a conical convergent jet whose apex is located inwardly of the discharge end of the tube in which the nozzle terminates. The nozzle includes a sleeve received in the tubular body and forming an annular channel with the wall of the body while a fitting is coaxial with the sleeve, delivers water under elevated pressure, and is threaded into the body.

Our present invention relates to devices for the generation of sand/water mixtures of high velocity for sandblasting and, more particularly, to improvements in the generation of such mixtures.

Sandblasting apparatus whereby sand or other granular or pulverulent material is entrained by a -uid at high velocity and directed from a nozzle against a surface to be treated are known in various forms. For the most part, such devices have made use of air under high pressure from a compressor or the like which was passed through a Venturi ejector through which a flow of the pulverulent material was induced by the Venturi suction. Where similar devices were employed with high-pressure water streams or other liquid media, it was found that the Venturi mixing devices were characterized by a rapidly developed blockage by sand at the inlets or outlets of the Venturi chamber. The deposition of sand within the mixing apparatus throttle the flow of the sandblast stream therethrough and sharply decreased the efficiency of the device. To a large measure, the development of blockages of this nature was a consequence of angular deflection of the throughow required by the usual Venturi or ejector mixer.

It is the principal object of the present invention to provide a device for the generation of sand/liquid mixtures for Sandblasting or the like which is free from the blockages and impediments characterizing previous devices and can be used with high-pressure streams without substantial loss of efficiency.

A further object of this invention is to provide in a hydraulic Sandblasting apparatus, an improved mixing device for sand and water streams.

These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, by a device for generating sand/ water mixtures and other high-velocity streams of pulverulent material and a liquid which comprises a mixing nozzle having a generally cylindrical passage, connecting means coaxial with the nozzle at a rearward end thereof for supplying to this passage a stream of sand or other pulver-ulent material, means forming within the nozzle a forwardly converging conical jet within the passage and coaxial therewith for inducing the stream of sand through the passage, the nozzle being forwardly opened for conducting the mixture of sand and water away from the jet.

ICC

Advantageously, the means for forming the conical water jet includes outlet means surrounding the sand stream and inclined forwardly and toward the axis, the passage having an extension beyond this outlet means such that the apex of the conical jet lies wholly within the passage. We have discovered that this arrangement permits the induction of the sand stream axially along the passage into the interior of the conical jet of water, and that the conical configuration of the jet and its location wholly within the extension of the axial passage ensures a thorough mixing of the sand lwith the water at high velocity. Furthermore, since the sand passes axially through the entire mixing nozzle, there are no deflections which can cause blockage or loss of efficiency in the mixing operation. The outlet means can include an annular slot or a multiplicity of angularly equispaced bores in a sleeve disposed within the body of the nozzle, the bores or slots communicating with an annular distributing channel surrounding the sleeve and the central passage therethrough. The slot then lies along the imaginary surface of the cone.

According to another feature of this invention, the annular (e.g. cir-cumferential) channel is defined between the sleeve and the inner Wall of the nozzle body and communicates with a generally radial port in the latter through which the high-pressure water is supplied to the nozzle. It has been found that this device can operate with water pressures of several hundred atmospheres. Best results are obtained with water pressures (at the inlet port) of upwards of 50 atmospheres (gauge) and, preferably, to several hundred of atmospheres. The device thus operates in accordance with an induction principle which does not depend upon Venturi effects and does not require the reflection of the sand stream before mixing with the fluid or thereafter. The extension of the passage, which also constitutes the outlet of the device, is preferably a tube threaded into the cylindrical nozzle body while the sleeve can be an insert axially movable therein and sealingly engaging the inner wall of the body on opposite sides of the channel or threaded into the body. Moreover, the means for supplying sand to the nozzle can be a fitting threadedly mounted in the mixing body. Thus, all of the components of the device are axially and coaxially interconnected. The distribution channel is, moreover, defined in part between axially spaced cylindrical bosses of the sleeve; it has been found that this arrangement precludes any significant erosion of the interior of the nozzle by the high-velocity sand stream in contrast with earlier systems in which such erosion rendered the nozzles inoperative or required frequent repairs of the device.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. l is an axial cross-sectional View of a mixing nozzle in accordance with this invention;

FIG. 2 is a cross-sectional view taken on the line II--II of FIG. 1; and

FIG. 3 is a fragmentary View of a modified nozzle arrangement in accordance with the present invention.

The mixing nozzle 1 of FIG. 1 is provided with a generally radial connecting pipe 2 which is welded to the nozzle body 9 in alignment with a radial port 1!) and serves to deliver water under an elevated pressure to the mixing nozzle. The body 9 is of a generally tubular, cylindrical configuration and is threaded at its right-hand end 12 to receive a connecting fitting 3 whose front end 13 is received within the cylindrical body 9 and whose rearward end 14 can be connected to a sand conduit in the usual manner. A shoulder 15 of the fitting 3 is of prismatic configuration for engagement with a wrench or other device for tightening the fitting 3 in the body 9. Within the axial passage 16 of the body 9, a sleeve 7 is inserted and is clamped against a shoulder 17 by the fitting 3. The sleeve 7 has a bore 18 in axial alignment with and of the same diameter as the axial bore 19 of the fitting 3 s0 that no shoulder or recess is provided at the contacting faces of the insert and fitting to cause accumulation of sand. A rubber seal 20 is recessed in the rearward end face of the insert 7 and abuts the front end face of the insert 3.

The insert 7 is provided with a pair of generally cylindrical bosses 21 flanking a circumferential groove 8 which defines with the wall 16 of the mixer body 9 an annular distribution channel communicating with the port 10. The bosses 21 are provided with O-ring seals 22 engaging the wall 16 to prevent leakage of the high-pressure liquid therepast. In the device of FIGS. 1 and 2, the outlet means for the high-pressure liquid is shown at to cornprise a multiplicity of angularly spaced 'bores converging beyond the axis A of the mixing nozzle, as represented by dot-dash line 6. The water jet from bores 5 forms a conical discharge, as represented at 6, convergent toward a point P within a tube 4 threaded into the forward end 23 of the nozzle body 9. The nozzle outlet tube 4 is thus coaxial with the passage defined by the bores 18 and 19 and is of a larger diameter than these 4bores so as to restrict lblockage of the passage by sand. The outlets 5 thus surround the bores 18 and 19 and are forwardly convergent so that their orientation is defined by the generatrices 6 of a cone whose apex is at P and whose base is represented at B. The diameter of the base B is preferably on the order on one-fourth to one-tenth the height H of the cone, the entire cone lying within the nozzle as defined by the body 9 and the tube 4.

The outlet means can also be formed as an annular slot 5' communicating with the channel 8', as indicated in FIG. 3. In this case, the sleeve is formed by a pair of concentric members 7a and 7b which are independently threaded into the bore 16' of the body 9 of the mixing nozzle. The sleeve portions 7a and 9a are beveled at Sa and 5b', respectively, to form the channel 5 which converges forwardly in the manner'represented yby the dot-dash line 6 of FIG. 1. While it has been noted that the apex P of the water jet should lie within the tube 4,

best results are obtained when the tube 4 terminates just 45 skilled in the art, all such modifications being considered within the spirit and scope of the appended claims.

We claim:

1. A mixing nozzle for generating a high-velocity stream of a granular material and a liquid, comprising an axially extending generally tubular body; connecting means at a rearward end of said body for supplying thereto an axial stream of said granular material in a generally forwardly direction; outlet means in said body surrounding said stream of granular material for discharging from all around said stream of granular material a conically convergent jet of high-pressure liquid in said forwardly direction for mixing said liquid with said material, said jet having an apex distal from said outlet means, said body being open in said forwardly direction; means on Said body for supplying high pressure liquid to said outlet means; and a discharge tube extending from the other end of said body in said generally forwardly direction just beyond the apex of said conically convergent jet, said outlet means including a sleeve received in said body and provided with a circumferential groove forming with an inner wall of said body an annular channel communicating with said means for supplying said liquid, said connecting means including a fitting coaxial with said sleeve and `said body and threaded into said body, said tube being coaxial with said sleeve and said body.

2. A nozzle as defined in claim 1 wherein said sleeve is provided with a multiplicity of angularly spaced bores inclined inwardly and forwardly from said channel.

3. A nozzle as defined in claim 1 wherein said outlet means includes an annular slot communicating with said channel and lying along a conical surface.

4. A nozzle as defined in claim 1 wherein said sleeve is slidably inserted in said body.

References Cited UNITED STATES PATENTS 2,392,408 1/ 1946 Radonich. 2,821,346 1/1958 Fisher 241--39 FOREIGN PATENTS 475,431 7/ 1951 Canada.

M. HENSON WOOD, IR., Primary Examiner. MICHAEL Y. MAY, Assistant Examiner.

U.S. Cl. X.R. 

